Wouldn't the most obvious explanation be a description which mentions Willy Wonka's chocolate factory, which doesn't really turn up anywhere in the training data except the original film media?

Star Wars is an interesting example because it appears to include elements lofted directly from the film (bits of stormtroopers body) alongside a princess who definitely isn't Leia. The algorithm might be creating things from scratch at a high level, but the constituent elements are pretty clearly close reproductions of parts of the source material